How to have data persist in GKE kubernetes StatefulSet with postgres? - postgresql

Question

So I'm just trying to get a web app running on GKE experimentally to familiarize myself with Kubernetes and GKE.
I have a statefulSet (Postgres) with a persistent volume/ persistent volume claim which is mounted to the Postgres pod as expected. The problem I'm having is having the Postgres data endure. If I mount the PV at var/lib/postgres the data gets overridden with each pod update. If I mount at var/lib/postgres/data I get the warning:
initdb: directory "/var/lib/postgresql/data" exists but is not empty
It contains a lost+found directory, perhaps due to it being a mount point.
Using a mount point directly as the data directory is not recommended.
Create a subdirectory under the mount point.
Using Docker alone having the volume mount point at var/lib/postgresql/data works as expected and data endures, but I don't know what to do now in GKE. How does one set this up properly?
Setup file:
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: sm-pd-volume-claim
spec:
storageClassName: "standard"
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 1G
---
apiVersion: "apps/v1"
kind: "StatefulSet"
metadata:
name: "postgis-db"
namespace: "default"
labels:
app: "postgis-db"
spec:
serviceName: "postgis-db"
replicas: 1
selector:
matchLabels:
app: "postgis-db"
template:
metadata:
labels:
app: "postgis-db"
spec:
terminationGracePeriodSeconds: 25
containers:
- name: "postgis"
image: "mdillon/postgis"
ports:
- containerPort: 5432
name: postgis-port
volumeMounts:
- name: sm-pd-volume
mountPath: /var/lib/postgresql/data
volumes:
- name: sm-pd-volume
persistentVolumeClaim:
claimName: sm-pd-volume-claim

Answer 1

You are getting this error because the postgres pod has tried to mount the data directory on / folder. It is not recommended to do so.
You have to create subdirectory to resolve this issues on the statefulset manifest yaml files.
volumeMounts:
- name: sm-pd-volume
mountPath: /var/lib/postgresql/data
subPath: data